Purchase this article with an account.
I. Quinones-Emmert, D. Rivera, R. Suarez, J. C. Zenteno; Molecular Screening of the VSX1, SOD1, and AQP5 Genes in Patients With Familial and Sporadic Keratoconus and Posterior Polymorphous Corneal Dystrophy. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1847.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Keratoconus (KC), the most common corneal dystrophy, is a disease in which the cornea develops a conical shape due to a noninflammatory thinning of the stroma. The estimated prevalence of KC is 1-4 per 2000 in the general population. The age of onset is often at puberty, and the disorder is progressive until the third or fourth decade of life when it usually arrests. KC is a major cause of corneal transplantation in developed countries. Most cases of KC are sporadic in occurrence although a positive familial history has been reported in at least 6-10% of patients. In addition, keratoconus prevalence in first degree relatives of KC patients is significantly higher than in the general population, demonstrating familial aggregation of the trait. Most published studies have suggested autosomal dominant inheritance of KC with incomplete penetrance or variable expression. Autosomal recessive inheritance as well as rare cases of X linked inheritance have also been described. Genetic factors clearly play a role, the pathogenesis of most cases of KC is unknown. Recently, point mutations in the VSX1 gene (Visual System Homeobox Gene 1) and an intronic deletion in SOD1 (superoxide dismutase 1) genes have been associated with some KC cases. On the other hand, absence of AQP5 (aquaporin 5) transcripts, a membrane protein regulating cell water transport, has been identified in corneal KC tissue. In this work we report the results of a screening of the VSX1, SOD1 and AQP5 genes in a group of 9 Mexican subjects with familial or isolated KC and the related posterior polymorphous corneal dystrophy (PPCD).
Nine individuals were included in the study: 5 diagnosed with familial KC, 3 with sporadic KC associated with PPCD, and 1 with isolated PPCD. Methods included complete ophthalmologic evaluation, genealogical analysis, and molecular screening of the VSX1, SOD1 and AQP5 genes coding regions and exon/intron junctions.
After sequencing the coding regions and exon/intron boundaries of the three KC-related genes, no deleterious mutations were found in any subject. Two intron 1-located variants were recognized in the AQP5 gene; however, the frequency of these variants in our KC patients appears to be the same in DNA from a control group.
Although our sample is small, results suggest that mutations in VSX1, SOD1 and AQP5 are not commonly associated to KC in our population. The genetic analysis of more numerous groups of KC patients from distinct ethnic origins will help to define the participation of these loci in KC pathogenesis.
This PDF is available to Subscribers Only